At 200 miles my 06 MCS developed a belt squeak. It only occurs off of idle as you rev the engine. When the car is started cold there is no squeak until the car warms up. It is not a constant squeak. It is more like a churping noise whose frequency increases as the revs increase. Any ideas? The tech at the dealer said it could be a bad belt. This conclusion was determined thru a phone diagnoses which is slightly better than useless. Since I am on the road, I have not been able to get it to the dealer for them to check it out. Kinda pisses me off that a NEW car has this annoying problem.
Justin

 

Stuff happens, a bad belt could show up on any car. You could try some belt dressing to see if that takes care of the noise. If it does, that confirms the belt as the culprit.

 

My 2005 MCSa does have a squeek at idle. I dont know if it squeeks after idle because I can only hear it outside the car. It probably does vary with RPM

It is pretty pronounced though.

As rhawth99 said, you could try some belt dressing.

I have an oil change commin up, so I'll ask then.

 

My belt squeeked for the first 1500 or so miles, it's been quiet the last 15500 miles I've owned it. I think it was from the stuff they spray on the car when it's put on the ship, my theory anyways.